This invention relates to stripe semiconductor laser structures, and more particularly to two stripe lasers in an integrated circuit with separate contacts for control current and with their ends at a cleaved face being disposed to emit their separate beams in an area sufficiently small (about 5 .mu.m) to couple both into a fiber optic. A further feature is that, when operating one below threshold while the other is operated above threshold, control of the one serves the longitudinal mode selection and tunability of the other laser.
It is well known that tandem coupled cavity lasers possess a high degree of selectivity compared to single cavity semiconductor lasers. This selectivity is due to the additional constraints imposed on the oscillation condition by the added cavity. By current control of the coupled (extra) cavity, it has been possible to tune the output of such lasers over significant regions. See W. T. Tsang, N. A. Olsson and R. A. Logan, "High-speed direct single-frequency modulation with large tuning rate and frequency excursion in cleaved-coupled-cavity semiconductor lasers," Appl. Phys, Lett. 42(8) Apr. 15, 1983, pp 650-52. An example is a semiconductor internal-reflection-interference (IRI) laser described by Hong K. Choi and Shyh Wang, Appl. Phys. Lett. 40(7), Apr. 1, 1982, at pages 571-73. In this particular case, the mode selectivity and tunability are affected by the interference which is caused by internal reflections from a transverse notch in the waveguide channel.
It has been reported recently by W. T. Tsang, et al., "Transient single-longitudinal mode stabilization in double active layer GaInAsP/InP laser under high-bit rate modulation," Appl. Phys. Lett. 42(12), June 15, 1983 at pages 1003-05 that longitudinal mode selectivity can also be achieved by coupling two or more semiconductor laser cavities in parallel. However, in that case the two cavities were not separately controlled.